1. Field of the Invention
This invention relates to an internal combustion engine and, in particular, to an arrangement for providing lubricant to a valve actuating mechanism of the internal combustion engine.
2. Description of the Related Art
The intake and exhaust valves of a typical four-stroke engine are opened and closed by a valve actuating mechanism. The valve actuating mechanism typically includes a cam shaft that is driven by a crankshaft. The cam shaft includes cam lobes that engage a follower mechanism for opening and closing the valves either directly or through an intermediate mechanism such as a tappet, a push rod or a rocker arm. The operating load on the valve actuating mechanism is particularly high especially in the area where the cam lobe contacts the follower mechanism. It is, therefore, necessary to provide lubricant to the valve actuating mechanism and, in particular, to the area where the cam lobe contacts the follower mechanism.
One arrangement for lubricating this area involves providing a lubricant passage in the cam shaft. The lubricant passage in the cam shaft communicates with a lubricant passage in the cam lobe, which has an opening located where the cam lobe contacts the follower mechanism. This arrangement, however, has several disadvantages. For example, when the cam lobe is not engaged with the follower mechanism, a substantial amount of lubricant is discharged through the opening on the cam lobe. This significantly reduces the lubricant pressure in the lubricant system. In addition, the edges of the opening can damage to the follower mechanism. Moreover, this arrangement provides little design flexibility with respect to where the lubricant is applied to the valve actuating mechanism.
Another arrangement for lubricating the valve actuating mechanism includes a lubricant pipe that is secured to the cylinder head by one or more supports. The lubricant pipe includes a lubricant passage and injection holes that are directed towards the valve actuating mechanism. Accordingly, lubricant flows through the lubricant pipe and is sprayed onto the valve actuating mechanism through the injection holes. Although this arrangement provides additional design flexibility, it also has several disadvantages. In particular, it is difficult to assemble and to disassemble. Moreover, because the pipe is secured directly to the cylinder, this arrangement is subjected to the vibration generated by the valve drive system.
It is, therefore, an object of the present invention to provide an improved arrangement for lubricating the valve actuating mechanism. Accordingly, one aspect of the of the present invention involves a four-cycle engine having a lubrication system. The engine comprises a cylinder block that has at least one cylinder. A piston is arranged for reciprocation within the cylinder and is connected to an output shaft. A head assembly is connected to the cylinder block. At least one combustion chamber is defined between the head assembly and the piston. At least one intake port and at least one exhaust port communicates with the combustion chamber. An intake valve is capable of closing and opening the intake port and an exhaust valve is capable of closing and opening the exhaust port. The engine also includes a valve actuating mechanism that includes an intake cam shaft capable of moving the intake valves and an exhaust cam shaft capable of moving the exhaust valves. A head cover is positioned over the valve actuating mechanism and defines, in part, a cam chamber. The lubrication system comprises a baffle plate unit located within the cam chamber above the valve actuating mechanism. The baffle plate unit includes a baffle plate that partially defines a path leading towards a discharge port for blow-by vapors from the combustion chamber. The baffle plate unit includes a lubricant passageway that is in communication with a lubrication system of the engine. The lubricant passageway is configured to supply lubricant to valve actuating mechanism.
Another aspect of the of the present invention involves a four-cycle engine that has a lubrication system. The engine comprises a cylinder block that has at least one cylinder. A piston is arranged for reciprocation within the cylinder and is connected to an output shaft. A head assembly is connected to the cylinder block. At least one combustion chamber is defined between the head assembly and the piston. At least one intake port and at least one exhaust port communicate with the combustion chamber. An intake valve is capable of closing and opening the intake port and an exhaust valve is capable of closing and opening the exhaust port. The engine also includes a valve actuating mechanism that includes an intake cam shaft capable of moving the intake valves and an exhaust cam shaft capable of moving the exhaust valves. A head cover is positioned over the valve actuating mechanism and defines, in part, a cam chamber. The lubrication system comprises a baffle plate unit that is located within the cam chamber generally above the valve actuating mechanism. The baffle plate unit includes a baffle plate that defines, along with the head cover, a path to a discharge port for blow-by vapors from the combustion chamber. The baffle plate unit includes means for the lubricating valve actuating mechanism.